Chances of a Bird Flu Pandemic and National Prevention Efforts
What changes are needed for H5N1 or another avian influenza virus to cause a pandemic?
Three conditions must be met for a pandemic to start: 1) a new influenza virus subtype must emerge for which there is little or no human immunity; 2) it must infect humans and causes illness; and 3) it must spread easily and sustainably (continue without interruption) among humans. The H5N1 virus in Asia and Europe meets the first two conditions: it is a new virus for humans (H5N1 viruses have never circulated widely among people), and it has infected more than 190 humans, killing over half of them. However, the third condition, the establishment of efficient and sustained human-to-human transmission of the virus, has not occurred. For this to take place, the H5N1 virus would need to improve its transmissibility among humans. This could occur either by "reassortment" or adaptive mutation. Reassortment occurs when genetic material is exchanged between human and avian viruses during co-infection (infection with both viruses at the same time) of a human or another mammal. The result could be a fully transmissible pandemic virus -- that is, a virus that can spread easily and directly between humans. A more gradual process is adaptive mutation, where the capability of a virus to bind to human cells increases during infections of humans.What is CDC doing to prepare for a possible H5N1 influenza pandemic?
CDC is taking part in a number of pandemic prevention and preparedness activities, including the following:
Providing leadership to the National Pandemic Influenza Preparedness and Response Task Force, created in May 2005 by the Secretary of the U.S. Department of Health and Human Services.
Working with the Association of Public Health Laboratories on training workshops for state laboratories on the use of special laboratory (molecular) techniques to identify H5 viruses.
Working with the Council of State and Territorial Epidemiologists and others to help states with their pandemic planning efforts.
Working with other agencies, such as the Department of Defense and the Veterans Administration, on antiviral stockpile issues.
Working with the World Health Organization (WHO) to investigate influenza H5N1 among people (e.g., in Vietnam) and to provide help in laboratory diagnostics and training to local authorities.
Performing laboratory testing of H5N1 viruses.
Starting a $5.5 million initiative to improve influenza surveillance in Asia.
Holding or taking part in training sessions to improve local capacities to conduct surveillance for possible human cases of H5N1 and to detect influenza A H5 viruses by using laboratory techniques.
Developing and distributing reagent kits to detect the currently circulating influenza A H5N1 viruses.
CDC has developed and is distributing the first FDA approved test for the detection of the H5 viruses that first emerged in Asia in 2003.
CDC also is working closely with WHO and the National Institutes of Health on safety testing of vaccine candidates and development of additional vaccine virus seed candidates for influenza A (H5N1) and other subtypes of influenza A viruses.
Source: U.S. Centers for Disease Control and Prevention
CDC.gov (www.cdc.gov) is your online source for credible health information and is the official Web site of the Centers for Disease Control and Prevention (CDC). CDC is committed to achieving true improvements in people’s health. CDC applies research and findings to improve people’s daily lives and responds to health emergencies—something that distinguishes CDC from its peer agencies. Working with states and other partners, CDC provides a system of health surveillance to monitor and prevent disease outbreaks (including bioterrorism), implement disease prevention strategies, and maintain national health statistics. CDC also guards against international disease transmission, with personnel stationed in more than 25 foreign countries.
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